brontozoum

from The Century Dictionary.

• noun A genus of gigantic animals, formerly supposed to be birds, now believed to be dinosaurian reptiles, known only by their tracks in the Triassic formation of the Connecticut valley. The stride was about 8 feet, and the length of the footprint about 17 inches.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Paleon.) An extinct animal of large size, known from its three-toed footprints in Mesozoic sandstone.